1. Field of the Invention
The present invention relates to a catalyst for homo-polymerization or co-polymerization of ethylene, or more particularly to a good-activity titanium solid complex catalyst supported in a carrier containing magnesium, the catalyst being capable of producing polymers of high bulk density with a narrow particle distribution and low contents of fine particles.
2. Description of the Related Art
Catalysts containing magnesium for polymerization or co-polymerization of ethylene are known to have very good catalytic activities and to accord good bulk density, which are suitable for liquid-phase or gas-phase polymerization. By liquid phase polymerization of ethylene, it denotes the polymerization process performed in such medium of bulk ethylene, isopentane, or hexane, and as for the important characteristics of the catalyst used in the process, they are as follows: high activity, bulk density, the amount of molecules of low molecular weight dissolved in a medium, particle distribution of polymers, the amount of fine particles, and so on.
Many of the titanium-based catalysts containing magnesium for olefin polymerization, and the manufacturing methods thereof have been reported. Especially, many processes making use of magnesium solutions to obtain olefin polymerization catalysts of good bulk density have been known. There is a means of obtaining a magnesium solution by reacting magnesium compounds with such electron donors as alcohol, amine, cyclic ether, or organic carboxylic acid in the presence of a hydrocarbon solvent. As for the cases of use of alcohol, they are disclosed in U.S. Pat. Nos. 4,330,649, and 5,106,807. Further, the methods for production of catalysts containing magnesium by reacting a magnesium solution with a halide compound such as titanium tetrachloride are well known. Such catalysts provide good bulk density, but there is much yet to be improved with respect to their catalytic activity and bulk density. Meanwhile, when the polymerization is carried out by means of using such catalysts, the resultant polymers have large amounts of fine powder with a broad particle size distribution and low bulk density. As such, there are serious defects with respect to productivity and handling at the time of processing.
To solve these problems, U.S. Pat. Nos. 3,953,414 and 4,111,835 disclosed a process for making catalysts for production of globular polymers with a very large average particle size by means of spray-drying magnesium dichloride hydrates. These processes, however, require much production facilities for catalysts such as spray-drying equipment and others, and the resultant catalysts have the disadvantages of low activities. Further, due to the existence of very large particles in polymers, there may arise problems at the time of the melting process.